Astrocytoma and ependymoma account for approximately 90% of spinal cord tumors (Table 24-1). Other tumors of the cord are rare. The presenting symptoms of spinal cord tumors are often nonspecific, and substantial delay in diagnosis is common. Typical early features are back pain, weakness, and clumsiness. Some patients develop torticollis or progressive scoliosis. Lumbar tumors can lead to bowel and bladder sphincter dysfunction. Clinical examination often demonstrates pathological reflexes and/or sensory change. MRI is the imaging technique of choice for the detection of these lesions.^1–9

Astrocytoma

Astrocytoma is the most common spinal cord tumor in children, accounting for approximately 60% of intramedullary neoplasms. This lesion results from the neoplastic transformation of astrocytes. Astrocytoma can arise in children of any age, including infants. The mean age at presentation in the pediatric age group is 6 to 7 years. There is no substantial gender predilection. The cervical and thoracic regions are the most common sites, although any portion of the cord can be involved. About half of spinal cord astrocytomas in children involve the entire cord, that is, holocord astrocytoma. Holocord astrocytoma is most common during the first year of life. Spinal astrocytoma can occur following radiation therapy; radiation-induced astrocytomas tend to be high-grade malignancies.^10–12

The clinical manifestations of spinal cord astrocytoma are variable. Potential findings include pain, gait disturbance (thoracic tumor), torticollis (cervical tumor), scoliosis, paralysis, hyporeflexia, sensory deficits, and sphincter dysfunction (lumbar tumor). There are 2 distinct clinical syndromes associated with holocord astrocytoma. (1) A lesion that is solid in the cervical region and cystic in the caudal portion of the cord most often results in unilateral upper extremity weakness, mild spastic weakness of the lower extremities, and (sometimes) neck pain. (2) When the major solid portion of the tumor is located in the thoracic or lumbar region, the major clinical finding is progressive spastic paraplegia, sometimes accompanied by thoracic pain and scoliosis. If the solid portion extends into the conus medullaris, lower extremity deep tendon reflexes are diminished and sphincter dysfunction is common.

Astrocytomas range from well differentiated to anaplastic types (grades I to IV). The aggressive malignant forms are more common in children than in adults. Malignant astrocytoma and glioblastoma account for up to one-quarter of astroglial spinal cord tumors in children. Astrocytomas are often infiltrative and are difficult or impossible to completely resect. The neoplasm causes diffuse enlargement of the involved portion of the cord; spread predominantly occurs in a longitudinal fashion. About two-thirds of spinal astrocytomas are predominantly solid; macroscopic cystic components are present in one-third. In comparison to ependymoma, spinal astrocytomas are less likely to be hemorrhagic or necrotic.

Radiographs of patients with spinal cord astrocytoma may show widening of the spinal canal and bony erosion. In the cervical region, this is best detected by an increase in the sagittal diameter of the canal and scalloping of the posterior surfaces of the vertebral bodies. In the thoracic and lumbar regions, the pedicles may be eroded and the spinal canal enlarged. Scoliosis occurs in some cases. Rarely, intraspinal calcifications are visible.

As with other cord tumors, myelography of patients with astrocytoma shows expansion of the involved segment of the cord. Occasionally, there is a complete block to the flow of subarachnoid contrast material. With CT myelography, low attenuation, nonenhancing cystic components may be visible within or adjacent to the intramedullary mass.

A spinal cord astrocytoma is usually isointense or hypointense to normal cord tissue on T1-weighted MR images and hyperintense on T2-weighted images (Figure 24-1). Perilesional edema also produces high signal intensity on T2-weighted images. There is enlargement of the involved segment of the cord, sometimes marked. The intensity and pattern of contrast enhancement vary between patients, and lack of enhancement does not exclude this diagnosis. Most often, at least a portion of the tumor enhances (Figure 24-2). Enhancement ranges from homogeneous to a patchy and irregular pattern similar to that of ependymoma (Figure 24-3). The margins tend to be poorly defined, particularly with high-grade tumors. Reactive edema in the adjacent cord parenchyma is usually present, and can be extensive (Figure 24-4). One or more tumoral cysts may be present. Intratumoral hemorrhage is unusual. Spinal cord astrocytomas are usually located eccentrically, a feature that is somewhat helpful in the differentiation from ependymomas, which tend to arise centrally (Figures 24-5 and 24-6).^13–15

Intramedullary cysts in patients with astrocytoma can occur within the tumor itself or in the cord parenchyma adjacent to the lesion. Benign cord cysts in these patients do not require resection, and are usually drained at the time of surgery. Both benign and neoplastic cord cysts typically produce low signal intensity on T1-weighted images and high signal on T2-weighted images, although necrosis or hemorrhage can alter the signal characteristics. Occasionally, a necrotic cyst may have similar signal characteristics as solid tissue on unenhanced images. The cavity of a cyst does not enhance. Neoplastic cysts tend to have an enhancing rim, whereas visible enhancement is typically lacking in the wall of a benign cyst. On unenhanced MR, the appearance of complex benign syringohydromyelia can overlap that of cystic astrocytoma on unenhanced MR; therefore, the use of intravenous contrast is generally indicated on the initial imaging evaluation of a complex syrinx that is not associated with Chiari malformation.

Ependymoma

Ependymoma is the second most common primary intramedullary spinal cord neoplasm in children, after astrocytoma. Ependymoma accounts for up to 30% of spinal cord tumors in children. The peak age at presentation is in early adolescence. About one-quarter of ependymomas arise in patients younger than 20 years of age. The filum terminale and conus medullaris are the most common sites, followed in decreasing order of frequency by the lumbar, thoracic, and cervical regions. Rarely, an ependymoma arises from ectopic ependymal cells along a nerve root within the cauda equina. Multifocal ependymoma of the spinal cord can occur in patients with neurofibromatosis type 2.¹⁶

Potential clinical manifestations of spinal ependymoma at the time of presentation include scoliosis, pain in the legs or back, paresthesias, and weakness in one or both lower extremities. The diagnosis may be delayed in those patients with scoliosis as the only symptom. All children with ependymoma eventually develop gait disturbances. The clinical features of spinal ependymoma vary somewhat according to the location of the tumor. Cervical lesions may lead to neck stiffness, torticollis, and neck pain that is worse at night. Lesions of the thoracic cord often produce pain localized to the level of the tumor. Ependymomas of the filum terminale may cause chronic low back pain, coccygodynia, or diffuse pain that radiates to the pelvis or lower extremities. Tumors of the filum terminale can rupture and cause subarachnoid hemorrhage, meningismus, fever, and cerebrospinal fluid (CSF) pleocytosis that mimics bacterial meningitis. Spastic paraplegia is a common finding on physical examination of children with ependymoma. Tumors in the cervical region sometimes cause weakness of one arm. Tumors of the cauda equina produce flaccid weakness and atrophy of the leg muscles, associated with loss of tendon reflexes. The CSF is often xanthochromic, and the protein content is elevated.

Spinal cord ependymomas are low-grade neoplasms; most are categorized as grade I or grade II lesions with the World Health Organization system. Those that arise in the filum terminale or conus medullaris are sometimes of the myxopapillary type, although this type of ependymoma is less common in children than in adults. Myxopapillary ependymomas are prone to hemorrhage. Those arising in the cervical region tend to be of the cellular type, with closely packed cells and a perivascular fibrillary appearance. Most spinal ependymomas arise from ependymal cells that line the central canal; therefore, these lesions tend to be located centrally within the cord. Spinal ependymomas are most often slowly growing neoplasms that compress adjacent normal spinal cord tissue, with little infiltration. Often, there is a delicate capsule that separates the tumor from adjacent cord tissue. This feature improves the feasibility of surgical resection. Cysts occur within the mass in about half of patients.¹³

Radiographs of patients with intraspinal ependymoma are often normal at the time of clinical presentation, although widening of the interpedicular distance and posterior vertebral scalloping can occur with lesions of long duration. Kyphoscoliosis is present in some patients. Myelography demonstrates a smooth or slightly lobulated intradural mass. The intramedullary nature of the mass may not be appreciable with lesions arising from the tip of the conus or the filum.

As with other neoplasms, ependymoma typically is isointense or hypointense on T1-weighted MR images and hyperintense on T2-weighted images. Peritumoral edema may lead to an overestimate of the size of the lesion on unenhanced T2-weighted images. Most spinal ependymomas are somewhat heterogeneous on MR, particularly those that arise in the conus and filum. Cysts are common, and may be located within the mass or adjacent to the cranial or caudal margins of the tumor (polar cysts). Hemorrhage and subsequent hemosiderin deposition sometimes create a hypointense rim at the periphery of the mass on T2-weighted images. When this occurs along the superior or inferior margin of the mass, it is termed the “cap sign.” Hypercellular regions within the tumor tend to be somewhat hypointense to the bulk of the lesion on T2-weighted images. The solid portions of ependymoma undergo intense contrast enhancement.¹⁷

Several imaging factors are helpful for the differentiation between spinal ependymoma and astrocytoma. Ependymomas tend to be more heterogeneous on MR imaging. Lower cord and filum terminale locations are more common with ependymoma. Astrocytoma tends to arise eccentrically within the cord and ependymoma centrally. Ependymomas are more frequently hemorrhagic. The plane of separation between tumor and adjacent benign cord tissue is usually better defined with ependymoma than with astrocytoma.

Surgical resection is indicated for the treatment of most spinal cord ependymomas. Polar cysts that are free of malignant cells on cytological examination do not require resection. Intratumoral cysts should be removed. With gross total resection of an encapsulated spinal ependymoma, the recurrence rate is approximately 15%.

Oligodendroglioma

Primary spinal cord oligodendroglioma is a rare glioma that accounts for less than 1% of all spinal cord tumors in children. This lesion can arise in patients of any age. There is no gender predilection. The most common location is in the thoracic segment of the cord, followed in frequency by the cervical and lumbar regions. Back pain is the most common presenting feature; other potential findings include motor deficits, paresthesias, paraparesis, sensory deficits, sphincter disturbances, and hyperreflexia.^3,18

Standard radiographs are usually normal at the time of clinical presentation in most patients with oligodendroglioma of the spine. Kyphoscoliosis is occasionally present. A large lesion sometimes leads to spinal canal enlargement and pedicle erosion. The MR features are similar to those of more common cord neoplasms, such as astrocytoma and ependymoma. This intramedullary tumor causes fusiform cord enlargement. Cysts can occur within or adjacent to the mass. The solid components enhance with contrast.

Ganglioglioma

Ganglioglioma is composed of both ganglion cells and glial cells, with the majority of glial cells being of the astrocytic subtype. This tumor can arise anywhere in the central nervous system; the temporal lobes of the cerebrum are the most common sites. Primary ganglioglioma of the spinal cord is uncommon. The mean age at presentation is approximately 12 years. Ganglioglioma is a low-grade neoplasm, and undergoes slow growth. The lesion is usually extensive by the time of clinical presentation, involving an average length of 8 vertebral segments.^19,20

The mixed composition of ganglioglioma results in a somewhat heterogeneous signal pattern on T1-weighted MRI images, and a patchy enhancement pattern. As with most neoplasms, ganglioglioma is hyperintense on T2-weighted images. Tumoral cysts are common; cysts are more common in ganglioglioma than in astrocytoma or ependymoma. Peritumoral edema is minimal. Because this is a slowly growing lesion, secondary vertebral abnormalities may be present at diagnosis, such as scoliosis and spinal canal expansion.

Patel et al noted the following features of ganglioglioma that aid in the differentiation from astrocytoma and ependymoma: long tumor length, presence of one or more tumoral cysts, presence of bone erosion and scoliosis, absence of edema, presence of mixed signal intensity on T1-weighted images, and presence of patchy enhancement and cord surface enhancement.¹⁹

Hemangioblastoma

Hemangioblastoma is a highly vascular endothelial cell neoplasm that most often occurs in the posterior fossa; 5% of these lesions arise in the spinal cord. Approximately two-thirds of spinal hemangioblastomas occur sporadically and one-third in association with von Hippel–Lindau disease. Patients with von Hippel–Lindau disease frequently have multiple hemangioblastomas; the spinal cord lesions in these patients are sometimes asymptomatic. When a small hemangioblastoma is symptomatic, there is frequently an associated syringomyelia. In the spine, hemangioblastoma most often arises in the subpial aspect of the dorsal cord; 10% to 20% of these tumors have combined intramedullary and intradural extramedullary components. The most common spinal location is the thoracic cord, followed by the cervical cord.

Hemangioblastoma is usually hypointense to isointense relative to normal cord tissue on T1-weighted MR images, and hyperintense to normal cord on T2-weighted images. Cysts are present in more than half of these lesions, sometimes occupying a greater area than the solid component; the signal characteristics of the tumoral cysts vary with the protein content. Substantial perilesional edema is typical. There is intense, homogeneous contrast enhancement of the solid tumor components. Flow voids from enlarged vessels may be visible within or adjacent to the lesion. The typical imaging features of hemangioblastoma vary somewhat with the size of the lesion. Those that are small (≤10 mm) are usually isointense on T1-weighted images, hyperintense on T2-weighted images, and undergo intense homogeneous contrast enhancement. Larger hemangioblastomas are often hypointense or mixed on T1-weighted images, heterogeneous on T2-weighted images, and enhance heterogeneously. Vascular flow voids are more often observed with large lesions. Small hemangioblastomas are usually located on the surface of the spinal cord, often posteriorly.^21,22

Primary Lymphoma

Primary intramedullary spinal lymphoma is extremely rare. This is a non-Hodgkin lymphoma. The lesion has very intense signal on T2-weighted images and undergoes prominent contrast enhancement. The mass is homogeneous and lacks necrosis.^23,24

Nerve Sheath Tumors

Nerve sheath tumors account for approximately 10% of pediatric spinal neoplasms. Schwannoma and neurofibroma are benign neoplasms of nerve root sheaths. There is histological overlap between these lesions. In general, schwannoma is a solitary encapsulated mass that does not completely surround the involved nerve root. Neurofibromas are usually multiple and completely envelop the involved nerve root. Schwannoma typically occurs as an isolated lesion or in association with neurofibromatosis type 2. Nearly all patients with neurofibromas have neurofibromatosis type 1. Neurofibroma is much more common than schwannoma in children. Neurofibrosarcoma is a rare malignant nerve sheath tumor. The most common clinical presentation of a nerve sheath tumor is that of pain and radiculopathy.

Schwannoma

Schwannoma (neurinoma, neurilemmoma) is a benign nerve sheath tumor. This lesion most often arises in the lower thoracic and lumbar portions of the spine. Malignant transformation is rare. Schwannoma is predominantly composed of Schwann cells, intermixed with fibrous tissue and adipose tissue. One or more cysts within the lesion are common. Typically, the lesion projects from the side of a nerve root and displaces normal nerve fibers.

Schwannoma is usually slightly hyperintense on T1-weighted MR images, and moderately hyperintense on T2-weighted images. In the central portion of the tumor, areas of collagen and Schwann cells may result in foci of T2 shortening. Contrast enhancement is typically homogeneous. Because of the nerve sheath origin, schwannoma is extramedullary and exophytic; a combination of intradural and extradural locations is common.

Neurofibroma

Neurofibroma is a peripheral nerve tumor that consists of fibroblasts and Schwann cells, intermixed between displaced nerve fibers. The mass usually has a fusiform shape. Nearly all patients with neurofibroma have neurofibromatosis type 1. Neurofibroma is one of several potential spinal abnormalities that can occur in children with this disorder (Table 24-2). Spinal neurofibromas in children with neurofibromatosis type 1 are often accompanied by scoliosis. The tumor can arise in any portion of the spine.

Neurofibroma is typically slightly hyperintense to muscle on T1-weighted MR images, apparently caused by mucopolysaccharides within the lesion. T2-weighted images typically show pronounced hyperintensity due to a high water content. Often, the periphery of the lesion produces higher signal intensity than the center on T2-weighted images, resulting in a target sign. Contrast enhancement is homogeneous. A symptomatic intradural neurofibroma is usually a dumbbell-shaped lesion that expands the involved neural foramen (Table 24-3). The mass follows the course of the nerve, and most often has intradural and extradural components. Early in the course, the lesion may be entirely intradural. Some paraspinal neurofibromas have no appreciable intraspinal extension.²⁵

Radiographic studies and CT of patients with spinal neurofibroma may show enlargement of one or more neural foramina, pedicle erosion, and focal enlargement of the spinal canal. Posterior vertebral body scalloping can also occur; it is important to recognize, however, that this is a common finding in patients with neurofibromatosis type 1 who do not have a space-occupying lesion. Paraspinal extension of a neurofibroma in the thorax can lead to rib erosions. Chest radiographs may show a paraspinal mass. In some patients, a paraspinal neurofibroma appears as an infiltrative retroperitoneal lesion, with encasement and displacement of the inferior vena cava and aorta. Associated scoliosis is common (Figure 24-7). Extensive involvement of nerves can occur, particularly in the neck and pelvis (Figure 24-8).

Neurofibrosarcoma

Neurofibrosarcoma (malignant schwannoma) is rare in children. Most of these patients have neurofibromatosis (type 1 or 2). Patients may present with pain, dysesthesias, and localized motor deficits. The imaging appearance of neurofibrosarcoma overlaps that of the benign nerve sheath tumors. The mass is hyperintense on T2-weighted images and often has a heterogeneous character. The target appearance that is common with neurofibroma is lacking with the malignant lesion. Neurofibrosarcoma is usually large at the time of diagnosis, and there may be a clinical history of rapid progression. Most often, the margins are somewhat irregular and infiltrative; however, some neurofibrosarcomas have well-circumscribed margins despite a large size of the tumor (Figure 24-9).

Drop Metastasis

There are 4 types of intradural spinal metastasis: subarachnoid metastasis, intradural extraarachnoid metastasis, invasion from an epidural lesion, and intramedullary metastasis. Intradural metastatic disease in children most often consists of subarachnoid drop metastasis from an intracranial neoplasm; intramedullary metastatic lesions are quite rare. The most common source of subarachnoid metastasis in children is medulloblastoma; other central nervous system primaries that may can produce drop metastasis include ependymoma, pineal neoplasms, high-grade astrocytoma, choroid plexus carcinoma, primitive neuroectodermal tumor and retinoblastoma.